The present invention concerns a device and a method for indication the current fatigue of a odontological instrument having at least a cutting zone and a handle.
In the odontological field surgeons use various instruments to excavate the dental canal before the introduction of a filling material into said dental canal.
The instruments to excavate the dental canal have to satisfy very high requirements. They must be sharp on at least a part of their length and their distal end have to be guided easily in the dental canal even when the canal has a small curve radius. To avoid the odontological instruments being broken in a dental canal they are mainly used manually rather than driven by a motor. Furthermore the screwing effect has to be avoided to reduce the tensions inside of the instruments. For these reasons this kind of instruments are known to be delicate.
In U.S. Pat. No. 5,628,674 it is known that a nickel and titanium alloy is adequate for the manufacturing of these instruments. It permit the realization of tools being resistant and supple allowing the use of motor driven odontological instruments. The instruments made of this alloy have an important drawback. Due to their resilience and their suppleness, the instruments do not present any lasting distortion indicating that they must be replaced. They remain identical and keep their aspect even when the limit of fatigue is reached. When the current fatigue becomes to high the instruments brake without showing any visible sign permitting to predict the moment when the braking occurs. Therefore the use of this type of instruments represent a number of serious problems for surgeons.
The object of the present invention is to overcome all these drawbacks and to realize a device permitting to give in a simple way an indication corresponding to the fatigue of an instrument, so that a user could replace the same before it represents a risk of breaking.
This object is reached by the device of the invention, characterized in that it comprises means connected to said odontological instrument indicating a value representing the current fatigue of said instrument, means for modifying said value based on parameters relating to the use of the odontological instrument and means for indicating that a limit value is reached.
According a preferred embodiment of the device of the invention, said means indicating a value representing the current fatigue of said instrument comprise a washer.
According to a first embodiment said washer is provided with a predetermined number of pre-perforations.
According to a second embodiment said washer comprises a predetermined number of detachable protrusions.
According to a special embodiment of the device of the invention said means indicating a value representing the current fatigue of said instrument comprises a code for identifying said instrument on an univocal way and for associating a value representing the current fatigue, and in that the device comprises a storage device for memorizing the current fatigue of each instrument.
According to an advantageous embodiment the device comprises a reading device for reading said code.
According to an advantageous embodiment the device comprises a stop washer said code being placed on said stop washer.
Said code is advantageously a bar-code.
Another object of the invention is a method for indication the current fatigue of a odontological instrument having at least a cutting zone and a handle, characterized in that it comprises a step of determining the value of current fatigue of the odontological instrument, a step of determining the value of fatigue corresponding to a specific use, depending of operational parameters of the instrument, a step of modifying the value representing the current fatigue according to the value of the fatigue induced by a specific use, depending of operational parameters of the instrument, a step of comparing the new modified value representing the new current value of fatigue of the instrument with a limit value.
According an advantageous embodiment of the device of the invention the curve radius of the dental canal is taken as an operational parameter of the instrument.
According another advantageous embodiment of the device of the invention the taper ratio of the instrument is taken as a operational parameter of the instrument.
According an advantageous embodiment of the device of the invention the duration of the operation corresponding to said specific use is taken as a operational parameter of the instrument.
According to a first manner to apply the method in which the odontological instrument comprises a washer provided with a number of pre-perforations the step of determining the value of current fatigue of the odontological instrument consists in realizing a number of perforations, this number depending of the value representing fatigue induced by the specific use.
According to a second manner to apply the method in which the odontological instrument comprises a washer provided with a number of detachable protrusions, the step of determining the value of current fatigue of the odontological instrument consists in detaching a number of protrusions, this number depending of the value representing fatigue induced by the specific use.
According to a third manner to apply the method in which the odontological instrument comprises a code, the step of modifying the value representing the current fatigue consists in modifying the value representing the current fatigue in the storage device, according to the value representing the fatigue induced by the specific use.